“To our knowledge, this is the first study to directly investigate the effect of both acute and short-term flavanol-rich cocoa (FRC) consumption on cerebral blood flow,”​ wrote lead author Farzaneh Sorond in the journal Neuropsychiatric Disease and Treatment​.

“We show that two weeks of regular FRC intake, providing 900 mg of cocoa flavanols daily, resulted in a significant increase in peak cerebral blood flow response in the middle cerebral artery.”​

The small study examined the effects of regular intakes of flavanol-rich cocoa (FRC) or flavanol-poor cocoa (FPC) in 34 healthy elderly volunteers with an average age of 72.

Researchers from Boston-based Hebrew SeniorLife, Beth Israel Deaconess Medical Center, and Brigham and Women’s Hospital, divided the volunteers into two groups. Thirteen people were assigned to consume FRC for two weeks and the blood flow in their brains was analysed. The other 21 participants were randomised to receive either daily FRC or FPC for one week in a double-masked, placebo-controlled, parallel-arm study.

Sorond and co-workers used ultrasound methods to measure the blood flow velocity in the middle cerebral artery (MCA).

In the 13 participants taking part in the first experiment, two-weeks of FRC (900 mg per day, Cocoapro, Mars) consumption was associated with a ten per cent increase in blood flow, said the researchers.

In the other experiment, one week of the FRC consumption was associated with an increase in blood flow of at least ten per cent in 55 per cent of the participants. FPC was associated with a blood flow increase in 10 per cent of the participants.

While the FRC increase was also larger (an average of 54 per cent compared to 16 per cent in the FPC group), large variation amongst the subjects meant that these differences were not statistically significant, added the researchers.

Mechanism​

The link between cocoa flavanols and cardiovascular health has been linked to the improving blood flow via increased production of nitric oxide (NO), a molecule used by the endothelium to signal surrounding muscle to relax.

“Based on early in vitro data that showed nitric oxide synthase [the enzyme that produces NO] activation by flavanols and our own work, which showed that FRC induced NO-dependent peripheral vasodilation in healthy humans, we propose that the cerebrovascular effects of FRC consumption are also NO-dependent,”​ stated the researchers.

“Studies using specific NOS inhibitors, such as N(G)-nitro-L- arginine methyl ester (L-NAME), will help to better define this pathway in the future.”​

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The researchers also noted that FRC contains some caffeine and theobromine, and that both compounds have been reported or suggested to be vasoconstrictors, thereby reducing blood flow.

“It is likely, therefore, that any increase in cerebral blood flow measured acutely following FRC consumption must emerge upon a background of vasoconstriction induced by its [caffeine and theobromine] ingredients,”​ they said.

Limitations​

Sorond and co-workers noted several important limitations with their study, including the lack of a control group in the two-week study. The researchers also did not impose any restrictions on the participants’ diets beyond advising the avoidance of cocoa and caffeine-containing products.

“With this information, we can proceed to determine the effect of FRC consumption on cerebral ischemic syndromes including stroke, vasospasm, and vascular cognitive impairment.”​

Commenting on the research, Harold Schmitz, PhD, chief science officer at Mars, said the study was “just one more study adding to an increasing body of literature connecting regular cocoa flavanol consumption to blood flow and vascular health improvements throughout the body." ​

"Though more research is needed, these findings raise the possibility that flavanol-rich cocoa products could be developed to help slow brain decline in older age," ​he said.